1. Field of the Invention
The present invention relates to a component mounting board structure having a heat radiation or heat block function and a production method thereof. The component mounting board structure is configured such that heat generated from a heat generating component, e.g., a heat generating element of an electronic device such as a switching regulator and a thermoregulator is efficiently radiated while does not have an influence on other components through a component mounting board.
2. Description of the Related Art
Recently, in the electronic devices such as the thermoregulator, development focuses on high functionality. However, heat radiation measures obstruct miniaturization and high performance of the electronic device.
In the heat radiation measures of the electronic device, there is a problem that electric power consumption of the electronic device is increased due to the high functionality of the electronic device, and thereby a temperature of an electronic component is increased to exceed a heat-resistant limitation temperature of the electronic component, namely, the temperature of the electronic component is increased not to be able to exert predetermined performance. From the standpoint of a demand of the miniaturization of the electronic device, there is also another problem that, because the same amount of heat is required to be radiated in an area smaller than ever, the heat is easy to accumulate in the device and thereby the temperature of the electronic component is increased to exceed the heat-resistant limitation temperature of the electronic component.
In the electronic devices such as the thermoregulator, plural components having large heat generation amounts are used in a power supply portion, though the power supply portion generates the largest heat generation amount. In order to eliminate the influence of the heat between components, it is necessary to increase a distance between components. Therefore, it is difficult to achieve the miniaturization of the electronic component. Further, because the heat radiation measures are achieved to all the plural components having large heat generation amounts, a production process becomes complicated, which obstructs improvement of production efficiency.
Therefore, in order to eliminate the influence of the heat generated by the heat generating component on other mounting components, there is a problem that heat block on a component mounting board is efficiently achieved while the miniaturization is realized. Under the situation that the modularization of the component mounting board is widely performed, in modularizing the component mounting board, it is necessary to develop the component mounting board from the viewpoint of controlling a heat radiation function.
Currently, in the case where the electronic components are mounted on the component mounting board and used in modules, a printed wiring board and lead frame board are frequently used as the component mounting board.
As is well known, the printed wiring board has a structure in which a metal thin plate formed by a copper plate or the like is laminated on a surface of resin board made of one kind of resin and a circuit pattern and the like are printed on the metal thin plate.
In the conventional heat generating component (heat generating element) in which the printed wiring board is used, there is a radiation structure in which the heat generated from the individual heat generating element is separately radiated through each radiator by providing the radiator in each heat generating component mounted on the printed wiring board.
For example, in the electronic component mounting, a through hole and plural screw holes are made in the printed wiring board, the heat generating element is mounted on one of surfaces of the printed wiring board corresponding to the through hole, a projection portion having a perforation and a screw locking hole are provided in the radiator, the projection portion is inserted into the through hole to arrange the radiator in printed wiring board corresponding to the position of the heat generating component, the screw inserted through the screw hole is fixed in the screw locking hole to attach the radiator to the printed wiring board, and a gap between the projection and an element package of the heat generating element is filled with a thermally conductive adhesive through the perforation using a syringe (for example, refer to Japanese Utility Model Application Laid-Open No. H06-45393).
The lead frame board in itself is formed by the metal thin plate such as the copper plate and an aluminum plate. The metal thin plate is punched to integrally provide a circuit pattern and a connection terminal by a pressing machine, the mounting components are soldered onto the circuit pattern, and the circuit pattern and the mounting component are sealed by an insulating resin layer made of one kind of insulating resin.
In the conventional heat generating component (heat generating element) in which the lead frame board is used, there is a radiation structure in which, while the high heat radiation function of the lead frame board is utilized to enhance the heat radiation function, similarly to the printed wiring board, the heat generated from the individual heat generating element is separately radiated through each radiator by providing the radiator in each heat generating component mounted on the lead frame board if needed (for example, refer to Japanese Patent Application Laid-Open Nos. 2003-347509 and 2003-243562).
Accordingly, in the configuration of the conventional techniques, both in the printed wiring board formed based on the resin board and in the lead frame board formed by sealing the circuit pattern and the mounting component with the insulating resin, the gap between the circuit patterns is insulated using one kind of resin, the heat generating components which generate the heat by themselves are treated irrespective of the different heat generating temperatures, and only the radiator is separately provided in each heat generating component to separately radiate the heat generated by the heat generating component using each radiator.
However, for the heat radiation problem of the electronic device having the configuration in which the mounting components are mounted on the component mounting board, it is necessary to manage design such that the temperature of the heat generating component does not exceed a heat-resistant limitation temperature of the heat generating component in consideration of the heat generated by each heat generating component. In addition, it is necessary to consider the following situation in order to completely solve the heat radiation problem.
That is, it is necessary to consider that the heat generated by the heat generating component has an influence not only on itself but on other mounting components.
In consideration of the above, for example, in the conventional techniques, there is known a technique in which a mounting area for the electronic components such as CPU having the large heat generating amount in the component mounting board and a mounting area where an imaging optical system and a solid-state imaging device are mounted are separated from each other by a notch, a metal member is inserted into the notch, and thereby the heat from the electronic components such as CPU is absorbed and radiated by the metal member inserted into the notch. There is also known a technique in which an electronic device housing is divided into a matrix, simple computation is performed by substituting attribute values (degree of heat generation, heat resistance, and criticality) for incorporated substances, and the result is compared to past successful records to determine arrangement of the incorporated substances in the electronic device housing (for example, refer to Japanese Patent Application Laid-Open Nos. H8-237525 and H9-230963).
However, in the conventional techniques, the arrangements of the heat generating component and the non-heat generating electronic component are designed on the component mounting board or in the electronic device housing by separating the heat generating component and the non-heat generating electronic component. That is, the mounting components having the functional correlations with one another are arranged in separate mounting areas in the component mounting board or electronic device housing, because mounting components differ from one another in the thermal property. Accordingly, in order to respond to the current demand of the high-density packaging, it is obvious that the conventional technique has a limitation.
In the conventional technique, the heat generating component is individually treated, and the radiation structure is formed for each heat generating component. Therefore, in the case where the heat generating components are collectively mounted in one area, it is not considered that the heat generated by one heat generating component has an influence on other heat generating components through the component mounting board.
The inventors do not focus on the heat radiation measures according to the arrangements of the mounting components mounted on the component mounting board, but the inventors focus on separate treatment of the heat generating component and the non-heat generating component. The heat generating component largely generates the heat by itself, namely, the heat generating component has a large self-heating characteristic. The non-heat generating component has no self-heating characteristic or hardly has the self-heating characteristic. The inventors also focus on a difference in heat-resistant limitation temperatures among the heat generating components and the non-heat generating components depending on the characteristics of the heat generating components and non-heat generating components.
The heat generating component is divided into a low heat-resistance heat generating component and a high heat-resistance heat generating component. The non-heat generating component is divided into a low heat-resistance non-heat generating component and a high heat-resistance heat generating component. In the radiation structure of the heat generating component, not only it should be considered that the heat generated by the heat generating component is not radiated only by the radiator individually provided in the heat generating component unlike the conventional technique, but also it should be considered that the heat generated by the high heat-resistance heat generating component has an influence on the low heat-resistance heat generating component through the component mounting board or the heat generated by the low heat-resistance heat generating component has an influence on the low heat-resistance non-heat generating component through the component mounting board.
In the case where the printed wiring board is used as the component mounting board formed by the high-density packaging, particularly in the case where the lead frame board is used as the component mounting board, the heat generated by the heat generating component is transferred to the lead frame board, so that the heat is easy to have an influence on other mounting components.
In view of the foregoing, an object of the invention is to provide a component mounting board structure having a heat radiation function or a heat block function. In the component mounting board structure, the mounting components mounted on the component mounting board are divided into the heat generating component and the non-heat generating component by distinguishing the heat generating components having large self-heating characteristics from the non-heat generating components having no self-heating characteristic or hardly having self-heating characteristics, the heat generating components are also divided according to the heat-resistant limitation temperatures, and thus various kinds of mounting components are separately treated. That is, the low heat-resistance heat generating component on which the heat has the largest influence is not affected by the heat generated by itself, the heat generated by the low heat-resistance heat generating component does not have an influence on the non-heat generating component, the heat generated by the high heat-resistance heat generating component does not have an influence on the low heat-resistance heat generating component, and the heat generated by the heat generating component, particularly by the low heat-resistance heat generating component is radiated by efficiently leading the heat to a point where the heat does not have an influence on neighbors, or the transferred heat is blocked, thereby suppressing the temperatures of all the mounting components to the heat-resistant limitation temperature or less.
Another object of the invention is to provide a method of producing a component mounting board structure having a versatile radiation structure according to the component mounting boards such as the printed wiring board and the lead frame board. In the component mounting board structure production method, the component mounting board structure is produced at low cost and improvement of assembling productivity is achieved. In the component mounting board structure, the mounting components mounted on the component mounting board are divided into the heat generating component and the non-heat generating component by distinguishing the heat generating components having large self-heating characteristics from the non-heat generating components having no self-heating characteristic or hardly having self-heating characteristics, the heat generating components are also divided according to the heat-resistant limitation temperatures, and thus various kinds of mounting components are separately treated. That is, the low heat-resistance heat generating component on which the heat has the largest influence is not affected by the heat generated by itself, the heat generated by the low heat-resistance heat generating component does not have an influence on the non-heat generating component, the heat generated by the high heat-resistance heat generating component does not have an influence on the low heat-resistance heat generating component, and the heat generated by the heat generating component, particularly by the low heat-resistance heat generating component is radiated by efficiently leading the heat to a point where the heat does not have an influence on neighbors, thereby suppressing the temperatures of all the mounting components to the heat-resistant limitation temperature or less.